A mechanical seal which is an example of a slide component is evaluated for its performance by a leakage rate, a wear rate, and a torque. In the conventional arts, by optimizing the seal material and the sliding surface roughness of mechanical seals, their performance is increased to achieve low leakage, long life, and low torque. However, due to growing awareness of environmental problems in recent years, a further improvement in the performance of mechanical seals has been demanded, for which technology development beyond the limits of the conventional arts has been required.
Conventionally, as the seal material of the mechanical seal, carbon, silicon carbide (SiC), cemented carbide and the like have been used. Among others, silicon carbide has been often used for the reason of being superior in corrosion resistance, wear resistance and the like (for example, see Patent Document 1 and Patent Document 2).
Moreover, since silicon carbide is a preferred material as the seal material of the mechanical seal but it is expensive and has poor workability, in order to be inexpensive, be more superior in corrosion resistance and wear resistance, and improve workability, a mechanical seal in which a sliding face of a seal ring is covered with diamond-like carbon (hereinafter, sometimes referred to as “DLC”) is proposed (for example, see Patent Document 3).
Further, in order to improve initial conformability of sliding faces of a seal ring of a mechanical seal, the mechanical seal in which the sliding face of the seal ring is covered with DLC is also known (for example, see Patent Document 4).